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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25236
Experience:  BMW Expert
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I'm driving a 3series convertible 02 reg but only 50 000 miles.

Customer Question

I'm driving a 3series convertible 02 reg but only 50 000 miles. Every so often (normally when it's relatively cold) the power completely cuts out and the battery light comes on for a second and then everything is fine. Really rather scarey - happened once at speed and the power didn't come back on. Is this alternator do you think? Battery quite new (replaced last year) so I know it's not that. any thoughts would be really helpful. thanks
Submitted: 2 years ago.
Category: BMW
Customer: replied 2 years ago.
I've been told it could be a faulty air filter but I don't feel very confident with that - why does it happen spasmodically? Doesn't happen that often, although yesterday it happened about 5 times (so suddenly much more frequently)
Expert:  Steve replied 2 years ago.
Does the engine cut out, or just electrical power?
Customer: replied 2 years ago.
Both - the engine cuts and there's no power. It feels as though it's "coughing" in that it hic-ups (with no power) and then it's all fine a second or two later. Very scary though - happened 3 times today, which is more frequent than it's been for a while
Expert:  Steve replied 2 years ago.
I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.
this would most likely be a fuel delivery interruption (failing fuel pump or blockage/filter), a spark issue (failing cam or crank sensor) or voltage issue (failing alternator or loose battery connection).
if the issue is happening this frequently this is a huge safety concern and you need to have the cause verified and rectified immediately. It should not be hard to have it diagnosed if it is happening this frequently, any trained bmw tech should be able to replicate and isolate the issue with basic checks/testing
Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.